What is the difference between believing in Allah and testifying that there is no deity worthy of worship except Allah in the Hadith of Jibril?

Praise be to Allah, and peace and blessings be upon the Messenger of Allah. To proceed:

At first glance, belief in Allah and the testimony of Tawḥīd may seem to be the same thing. However, the Islamic texts show that the relationship between them depends on the context in which they are mentioned.

When Islam and faith (Īmān) are mentioned together, they have distinct meanings

In the Hadith of Jibril, Jibril asked the Prophet ﷺ first about Islam and then about faith (Īmān). The Prophet ﷺ explained that:

• Islam begins with the testimony of faith, establishing prayer, paying zakāh, fasting Ramadan, and performing Hajj.
• Faith (Īmān) is belief in Allah, His angels, His books, His messengers, the Last Day, and the Divine Decree, both its good and what is perceived as its hardship.

Therefore, the scholars explained that when Islam and Īmān are mentioned together, each has a specific meaning:

• Īmān relates to the actions of the heart, such as belief, certainty, sincerity, and affirming Allah's Lordship, His sole right to be worshipped, and His Names and Attributes.
• Islam relates to the outward actions through which a servant submits to Allah, beginning with the testimony of faith and followed by the rest of the pillars of Islam.

The inward and outward are inseparable. The faith of the heart is not valid without outward actions that reflect it, and outward actions are of no benefit if the heart is devoid of faith.

When one of the two terms is mentioned alone, it includes the other

If the word Īmān is mentioned by itself, it includes the entire religion: belief, speech, and actions.

For this reason, the Prophet ﷺ said to the delegation of ʿAbd al-Qays:

"I command you to have faith in Allah."

He then explained this by mentioning the testimony of faith, prayer, zakāh, and other acts.

Likewise, the Prophet ﷺ said:

"Faith consists of more than seventy branches, the highest of which is saying: 'There is no deity worthy of worship except Allah'..."

Thus, he counted the testimony of faith as one of the branches of Īmān, because when Īmān is mentioned alone, it includes it.

Why do the definitions differ in the texts?

There is no contradiction. Rather, this follows a well-known principle of Ahl al-Sunnah:

• When Islam and Īmān are mentioned together, they have distinct meanings.
• When either one is mentioned alone, it includes the other.

In other words, when one term appears independently, it encompasses the whole religion. When both appear together, each carries a specific meaning.

This principle was affirmed by many scholars, including Al-Ismāʿīlī, Al-Khaṭṭābī, Ibn Rajab, and others.

What is the difference in brief?

It may be summarized as follows:

• Belief in Allah is the firm conviction of the heart, affirming Allah's Oneness, His Lordship, His exclusive right to be worshipped, and His Names and Attributes.
• The testimony that there is no deity worthy of worship except Allah is the outward declaration of that belief through speech. It is the first outward act by which a person enters Islam.

Thus, when both terms are mentioned together, Īmān refers primarily to the inward reality, while Islam refers primarily to the outward submission. When either term appears alone, it includes the entire religion.

Conclusion

There is no contradiction between belief in Allah being the first pillar of faith and the testimony that there is no deity worthy of worship except Allah being the first pillar of Islam.

When Islam and Īmān are mentioned together, Īmān relates to the actions of the heart, while Islam relates to outward actions. When either one is mentioned independently, it includes the other, because faith in Islam consists of belief in the heart, affirmation by the tongue, and actions of the limbs, all of which are inseparably connected.

And Allah knows best.